Actually at least S50, S52 and S54 engines are pretty different than M50-based M52 and M54. S-series didnīt share same block, crank, pistons, head, intake manifold etc. You can check it in Realoem.com.

It's no secret that the S engines were "derived" from their non-M counterparts. That doesn't mean the same exact materials have to be used.